linux-kernel - Re: [RFC PATCH v5 2/6] mtd: rawnand: meson: wait for command in polling mode

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Message-ID: <c316961d-6021-1cb4-9ff4-22fe9ca5a18a@sberdevices.ru>
Date:   Mon, 5 Jun 2023 19:58:02 +0300
From:   Arseniy Krasnov <avkrasnov@...rdevices.ru>
To:     Liang Yang <liang.yang@...ogic.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
CC:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        <oxffffaa@...il.com>, <kernel@...rdevices.ru>,
        <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v5 2/6] mtd: rawnand: meson: wait for command in
 polling mode



On 05.06.2023 16:30, Liang Yang wrote:
> 
> 
> On 2023/6/5 21:19, Liang Yang wrote:
>> Hi Miquel and Arseniy,
>>
>>
>> On 2023/6/5 17:05, Miquel Raynal wrote:
>>> [ EXTERNAL EMAIL ]
>>>
>>> Hi Arseniy,
>>>
>>>>>> @@ -1412,6 +1419,8 @@ static int meson_nfc_probe(struct platform_device *pdev)
>>>>>>             return ret;
>>>>>>     }
>>>>>>
>>>>>> +  nfc->use_polling = of_property_read_bool(dev->of_node, "polling");
>>>>>
>>>>> This is a problem. You cannot add a polling property like that.
>>>>>
>>>>> There is already a nand-rb property which is supposed to carry how are
>>>>> wired the RB lines. I don't see any in-tree users of the compatibles, I
>>>>> don't know how acceptable it is to consider using soft fallback when
>>>>> this property is missing, otherwise take the values of the rb lines
>>>>> provided in the DT and user hardware control, but I would definitely
>>>>> prefer that.
>>>>
>>>> I see. So i need to implement processing of this property here? And if it
>>>> is missed -> use software waiting. I think interesting thing will be that:
>>>>
>>>> 1) Even with support of this property here, I really don't know how to pass
>>>>     RB values to this controller - I just have define for RB command and that's
>>>>     it. I found that this property is an array of u32 - IIUC each element is
>>>>     RB pin per chip. May be i need to dive into the old vendor's driver to find
>>>>     how to use RB values (although this driver uses software waiting so I'm not
>>>>     sure that I'll find something in it).
>>>
>>> Liang, can you please give use the relevant information here? How do we
>>> target RB0 and RB1? It seems like you use the CS as only information
>>> like if the RB lines where hardwired internally to a CS. Can we invert
>>> the lines with a specific configuration?
>>
>> Controllor has only one external RB pinmux (NAND_RB0). all the RB pins
>> of different CEs need to be bound into one wire and connect with
>> NAND_RB0 if want to use controller polling rb. the current operating
>> CE of NAND is decided to "chip_select", of course controller internally has different nfc commands to regconize which Ce's RB signal is polling.
>>
>> <&nand_pins> in dts/yaml should include the NAND_RB0 if hardware connects, or use software polling here.
>>
>> @Arseniy, sorry, i don't travel all the informations yet. but why don't you use the new RB_INT command with irq that i provided in another thread. the new RB_INT command doesn't depend on the physical RB wires, it also send the READ status command(0x70) and wait for the irq wake up completion.

Technically no problem! I can use new RB_INT instead of 'nand_soft_waitrdy()' as software fallback, and currently
implemented RB_INT as interrupt driven way. What do You think Miquel ?

> 
> Use "nand-rb" in dts to decide old RB_INT(physical RB wires is needed) or new RB_INT(no physical RB wires). the new RB_INT command decides the RB0 or RB1 by the previous command with ce args.
> 

So I can implement "nand-rb" in dts as boolean value - "false" or missing means use "no physical RB wires", "true" - means use "physical RB wires" ?

Thanks, Arseniy

>>
>>> Arseniy, if the answer to my above question is no, then you should
>>> expect the nand-rb and reg arrays to be identical. If they are not,
>>> then you can return -EINVAL.
>>>
>>> If the nand-rb property is missing, then fallback to software wait.
>>>
>>>> 2) I can't test RB mode - I don't have such device :(
>>>>
>>>> Also for example in arasan-nand-controller.c parsed 'nand-rb' values are used
>>>> in controller specific register for waiting (I guess Meson controller has something
>>>> like that, but I don't have doc). While in marvell_nand.c it looks like that they parse
>>>> 'nand-rb' property, but never use it.
>>>
>>> Yes, the logic around the second RB line (taking care of CS1/CS3) is
>>> slightly broken or at least badly documented, and thus should not be
>>> used.
>>>
>>>>> In any case you'll need a dt-binding update which must be acked by
>>>>> dt-binding maintainers.
>>>>
>>>> You mean to add this property desc to Documentation/devicetree/bindings/mtd/amlogic,meson-nand.yaml ?
>>>
>>> Yes. In a dedicated patch. Something along the lines:
>>>
>>>          nand-rb: true
>>>
>>> inside the nand chip object should be fine. And flag the change as a
>>> fix because we should have used and parsed this property since the
>>> beginning.
>>>
>>> Thanks,
>>> Miquèl